Mitigating the autogenous shrinkage of ultra-high performance concrete by using rice husk ash

Concrete made with Portland cement has good behaviour under compressive stress, but it is weak in tension. Cracking caused by tension is a typical problem in concrete practice. High autogenous shrinkage at early ages is one of the causes of cracking, especially in high/ultra-high performance concrete. In that stage shrinkage is strongly related...

Effect of Activator and Mineral Admixtures on the Autogenous Shrinkage of Alkali-Activated Slag/Fly Ash

The high autogenous shrinkage of alkali-activated fly ash/slag (AASF) poses a significant concern for the widespread application of AASF in structural engineering. The present study compares the efficacy of activator and mineral admixtures in mitigating the autogenous shrinkage of AASF, and discusses the underlying mechanism. The results show...

Influence of the Ms-modulus on the early-age volume change and heat release of slag and fly ash pastes activated by sodium hydroxide and sodium silicate

Blended pastes composed of slag and fly ash (ratio 50:50) are used with sodium hydroxide and sodium silicate as precursors. Each composition has the same solution to binder ratio (S/B) and the Ms-modulus varies between 1.04 and 1.58. All the experiments were conducted at a constant temperature of 20°C. The physical mechanisms related to the...

Autogenous shrinkage of alkali-activated slag and fly ash materials: From mechanism to mitigating strategies

Alkali-activated materials (AAMs), as eco-friendly alternatives to Ordinary Portland cement (OPC), have attracted increasing attention of researchers in the past decades. Unlike cement, which requires calcination of limestone, AAMs can be made from industrial by-products, or even wastes, with the use of alkali-activator. The production of AAMs...

Mitigating the autogenous shrinkage of alkali-activated slag by internal curing

Alkali activated slag (AAS) has shown promising potential to replace ordinary Portland cement as a binder material. Synthesized from industrial by-products, AAS can show high strength, thermal resistance and good durability. However, AAS has been reported to exhibit high autogenous shrinkage. Autogenous shrinkage is a critical issue for building...

Autogenous shrinkage of early age cement paste and mortar

Concrete is a brittle composite material that easily fractures under tension. Due to the fact that the early-age deformation of the concrete member is restrained by adjoining structures, cracking can occur throughout the concrete prior to application of any load. The cracks would provide preferential access for aggressive agents penetrating in...

Setting, Strength, and Autogenous Shrinkage of Alkali-Activated Fly Ash and Slag Pastes: Effect of Slag Content

The engineering properties of alkali activated materials (AAMs) mainly depend on the constituent materials and their mixture proportions. Despite many studies on the characterization of AAMs, guidelines for mixture design of AAMs and their applications in engineering practice are not available. Extensive experimental studies are still necessary...

Use of rice husk ash for mitigating the autogenous shrinkage of cement pastes at low water cement ratio

It is well recognized that the high risk of early age micro-crack of HPC/UHPC is attributed to the large magnitude of early age autogenous shrinkage caused by self-desiccation in binder hydration. Over the years, several methods have been proposed to mitigate autogenous shrinkage based on internal curing theory, and a better internal curing...

Time- and load- dependent behaviour of flowable concrete: Progress report of fib task group 4.3

Stress and strain interaction is of vital importance for concrete structures as it has an influence on cracking, deflection and prestressing loss. With the increased range of compressive strengths and flow characteristics, the mixture composition of nowadays concretes often differs considerably from Vibrated Concrete (VC) with regard to paste...

Viscoelastic stress modeling in cementitious materials using constant viscoelastic hydration modulus

Viscoelastic stress modeling in ageing cementitious materials is of major importance in high performance concrete of low water cement ratio (e.g. w/c ~0.35) where crack resistance due to deformation restraint needs to be determined. Total stress analysis is complicated by the occurrence of internal stresses due to shrinkage, which requires...

Modeling and analyzing autogenous shrinkage of hardening cement paste

In this paper, a conceptual model for analyzing the plastic part of autogenous deformation of cement paste based on the Arrhenius rate theory will be presented. The autogenous deformation will be calculated from the elastic deformations with inclusion of creep. Different kinds of cement paste with a water cement ratio 0.3 are tested and studied,...

Ultra high performance concrete made with rice husk ash for reduced autogenous shrinkage

Ultra High Strength Concrete (UHPC) is generally made with low w/c mixtures and by adding silica fume. Low w/c mixtures, however, exhibit high autogenous shrinkage, while a high amount of silica fume increases the price of these mixtures. For designing ultra high strength mixtures with low autogenous shrinkage and lower costs the possibility of...

Autogenous Deformation and Internal Curing of Concrete

High-performance concrete (HPC) is generally characterized by a low water/binder ratio and by silica-fume addition, which guarantee a low porosity and a discontinuous capillary pore structure of the cement paste. Modern concretes possess some highly advantageous properties compared to traditional concrete, such as good workability in the fresh...

Numerical modelling of self-desiccation of hardening cement paste

In this paper a numerical model is presented with which it is possible to predict the non-thermal hydration-induced volume changes that develop during hardening of a cement-based material. The model equilibrates the relative humidity in the pore system with the free surface energy in hardening cement past. From a certain state of equilibrium,...